The aim of this project is to understand the development of social information processing in children and the relation between information processing and the development of social competence and peer relations in children. Toward this end, four programs of research are proposed. In the first program, a model of social informatin processing will be articulated. The role of negative affect in disrupting rational processing among socially incompetent, agressive children will be tested through experimental studies. The second program will examine the developmental origins of social information processing patterns through two longitudinal studies. The first study is a four-year investigation of 600 four-year-old children in which early socialization experiences will be related to the emergence of aggressive behavior and deficits in social information processing. Several theoretical models of the development of processing patterns will be evaluated. In the second study, the unfolding relation between biases in social information processing about peers and agressive interpersonal behavior will be examined by observing children during their initial play encounters and interviewing them repeatedly over a five-day period. The aim of the third program is to identify the peer perceptual bases and behavioral bases for social rejection among urban black children who are at social risk. Play groups of children will be formed and observed over a five day period. Children's perceptions of the bases for social rejection and children' processing of social information about peers' play will be evaluated through experimental interviews. The fourth program will identify factors in school-aged children which place them at risk for later maladjustment. This program is a continuation of a ten-year longitudinal study of 500 children. As a whole, these programs will contribute to our understanding of basic processes of children's social development, particularly the development of soical information processing patterns and peer relations. These programs will also lead to the design of interventions aimed at preventing the development of aggressive behavior problems.